Set junit4 version where used. Fixes #2289

[barchetta]

Fixes #2289

I did not put the junit 4 version in dependency management since Helidon uses Junit 5. Instead the version is specified in the one place where it is needed.

[barchetta]

mvn org.apache.maven.plugins:maven-help-plugin:3.2.0:effective-pom -Dverbose shows:

  <dependencyManagement>
    <dependencies>   
. . .
      <dependency>
        <groupId>junit</groupId>  <!-- com.fasterxml.jackson:jackson-parent:2.11, line 76 -->
        <artifactId>junit</artifactId>  <!-- com.fasterxml.jackson:jackson-parent:2.11, line 77 -->
        <version>4.12</version>  <!-- com.fasterxml.jackson:jackson-parent:2.11, line 78 -->
      </dependency>
    </dependencies>
  </dependencyManagement>